Patterns for a tree of persistent data with multiple storage options?@occulus but people do have favourite hammers, because with the proliferation of hammers out there, they can be similar but vary slightly. The same is true of design patterns. As there is no absolute authoritative source for all "approved" design patterns (not everything is in Gang of Four), there are loads of slightly different but very similar ones created by different communities. When I say my favourite I mean I think it's the neatest but I recognise other people have other opinions. It would be the same with a hammer. However I'm willing to accept if in this case my choice is just wrong